Polysaccharides are used in, for example, medical products. One reason for the addition of the polysaccharides to medical products is to give the medical products a higher viscosity. This is needed in for example tissue treatment compositions, such as adhesive compositions in order to make them easier to handle. The polysaccharides may in some cases be mixed with some proteins and they usually need to be sterilized when used in a medical product.
Proteins are sensitive to heat and cannot be heat sterilized, and they are usually filter-sterilized. However, polysaccharides are not possible to filter-sterilize due to the high viscosity and the high molecular weight of these substances. Hence, there is a need to sterilize polysaccharides in order to be able to use them in medical products. However, polysaccharides are also heat sensitive and they are degraded by heat and especially if they have to spend a long time under heat treatment. If they are degraded, they will loose viscosity and would not be as useful any longer or could not be used at all.
Heat sensitive products have been sterilized in some different ways. WO 00/24433 describes a method of reducing degradation of heat sensitive components, such as glucose, in medical substances during heat sterilization. This is made by using a multiple chamber recipient that comprises a first chamber with a first medical substance and at least one second chamber containing an amount of a second medical substance that is smaller than that of the first medical substance. The first chamber is heated to a predetermined temperature for sterilizing the medical substances, and the second chamber is thermally insulated during heating of the multiple chamber recipient. The thermal insulation of the second chamber is removed so that a defined hold time of the second chamber at the sterilization temperature is obtained. The content of the different chambers may then be mixed together.
The process according to the invention especially relates to autoclaving of hyaluronic acid. U.S. Pat. No. 5,621,093 describes a way of steam-sterilizing solid hyaluronic acid in order to overcome disadvantages with chemical sterilization, dry heating and sterilizing hyaluronic acid in solution. These may cause chemical contamination and reduction in molecular weight.
Healon® is the brand name of a product comprising hyaluronic acid, manufactured by Pharmacia AB, and Healon® is sterilized in small glass vessels with a volume of about 1 ml. Hence, these vessels are very small. There is now a need of bulk autoclaving polysaccharides, and especially hyaluronic acid. The purpose with the invention is to solve the problems mentioned above, and reduce the viscosity decrease in bulk autoclaving, which has not been possible before.